havent played a pokemon game since emerald so this is a surprise to me
It's a forced catch that's why it's easy. Even if you faint it or run away, you're forced to battle him again.
this is all new to me. what is life?
Black and White did this as well with Zekrom and Reshiram as storywise the legendary wants to join you. Iirc Dialga and Palkia in Diamond and Pearl also had a better catch rate than normal though I dont remember if they had a reason for that --- Ryuho, Playing Tales of Graces F Forever in my heart.